SATURATED MEDIA EXTRACT TESTING FOR GREENHOUSE SOILS 

As of September 2005, the University of Connecticut Soil Nutrient Analysis Laboratory replaced the more limited Spurway Analysis with Saturated Media Extract (SME) testing for greenhouse soils. SME is currently used by most commercial soil and fertilizer testing facilities as well as by many university laboratories. 

Testing the growing media for nutrients, pH and soluble salts is beneficial to the commercial grower because:

• Testing can evaluate the nutrient status of crops.
• Testing can aid in diagnosis of plant problems.
• Testing can prevent plant problems from developing.
• Testing can be used to evaluate current fertilizer practices.
• Testing is an important component of integrated crop management programs.
• Testing alerts growers to potential environmental hazards i.e. nutrient runoff.

The SME, like most soil fertility tests, measures the amount of plant available nutrients in the growing media. It differs from the Spurway method both in how nutrients are extracted from the media and also in the number of essential elements available from this procedure. Routine SME tests will now include pH, soluble salts, calcium, magnesium, potassium, phosphorus, copper, zinc, iron, manganese, boron, molybdenum, nitrate-nitrogen, and ammonium-nitrogen. The cost is presently $5 per sample but note that fees will increase slightly in January.  

With the SME method a large sample (1 – 1 ½ cups) of growing media, exactly as received from the grower, is used for analysis. This reduces sampling preparation error as no preliminary handling of the sample is necessary. Also, with no preliminary sample preparation, the soil test results are not unreasonably inflated if a few slow release fertilizer prills happen to be present. 

The actual methodology involves first saturating the sample with distilled water and then allowing it to equilibrate. The liquid extract is then collected and this extract contains the nutrients that potentially should be available to the plants. Analysis for pH, soluble salts and nutrients are all performed either on the slurry or extract created using this procedure. 

SOIL SAMPING INSTRUCTIONS

When collecting samples for the SME analysis, it is important not only to collect a representative sample but also to provide the laboratory with an adequate sample size. 

Please note: Unless a representative soil sample is taken, the analysis and interpretation are of no value. 

Follow these simple directions:

1)      WHEN TO SAMPLE DEPENDS ON YOUR FERTILIZER REGIME:

For constant liquid feed or regular periodic liquid feeds (i.e. once a week) take samples about 4 hours after fertilizing or at least the same day.

For crops with slow release fertilizer that receive infrequent fertilizer supplements, sample 4 hours after watering.

2)      Always be consistent in sampling protocol if reports are to be compared.

3)      SPECIAL PROCEDURES FOR COLLECTING SAMPLES:

Bench Crops: Take a full core of potting medium from top to bottom of bench from 10 locations. Mix in clean container.

Potted Plants:  Take slices from side of root ball from 10 or more pots. Mix in clean container

Potting or Transplanting Mixes or Compost Pile:  Take small portions from 10 or more locations in pile. Mix in clean container.

Never sample from just the top 1/3^rd of pot, results will overestimate fertility.

4)      Remove slow release prills as best as possible.

5)      Transfer 1 ½ to 2 cups of the potting mixture from the clean container to a zipper-lock bag, and label the outside of the bag with a sample name or number.

6)      Samples may be brought or mailed to the Soil Nutrient Analysis Laboratory along with a filled out greenhouse questionnaire and payment. Contact the lab if you are interested in purchasing prepaid soil collection kits.

7)      A copy of the results of the analysis will be sent to you. Results can also be faxed upon request. IF YOU WOULD LIKE TO RECEIVE FERTILIZER RECOMMENDATIONS MADE BY DR. RICHARD MCAVOY, EXTENSION SPECIALIST – GREENHOUSE CROPS, BE SURE TO CHECK OFF THE APPROPRIATE BOX ON THE QUESTIONNAIRE. RECOMMENDATIONS WILL BE INCLUDED ONLY IF A RECOMMENDATION IS REQUESTED. 

11/05 Presented at the Greenhouse Tomato Conference sponsored by University of Connecticut Cooperative Extension System, NE SARE and UMass Extension.  

UNIVERSITY OF CONNECTICUT
DEPARTMENT OF PLANT SCIENCE
SOIL NUTRIENT ANALYSIS LABORATORY
6 Sherman Place, Unit 5102, Storrs, CT 06269-5102 ● Phone (860)486-4274, Fax (860) 486-4562

The information in this material is for educational purposes. The recommendations contained are based on the best available knowledge at the time of printing. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension system does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations as of the date of printing. If the information does not agree with current labeling, follow the label instructions. The label is the law.Warning! Agrochemicals/pesticides are dangerous. Read and follow all instructions and safety precautions on labels. Carefully handle and store agrochemicals/pesticides in originally labeled containers immediately in a safe manner and place. Contact the Connecticut Department of Environmental Protection for current regulations.The user of this information assumes all risks for personal injury or property damage.Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kirklyn M. Kerr, Director, Cooperative Extension System, The University of Connecticut, Storrs. The Connecticut Cooperative Extension System offers its programs to persons regardless of race, color, national origin, sex, age or disability and is an equal opportunity employer.